A great deal can be learned about plasticity in the developing human nervous system by studying children who incur brain insults during critical periods of brain development. Damage to the developing brain may have a very different impact on cognition than would damage to the fully developed brain. The focus of this study will be to evaluate the role of seizures and of epileptiform brain activity on cognitive function in children with early focal brain damage (FL). The study proposes to explore issues of plasticity and reorganization in the developing human brain by studying children who suffered very early unilateral brain damage from stroke or hemorrhage, incurred prior to or at birth. The specific aims of the project are 1) to determine the impact of seizures and of epileptiform brain activity on cognitive outcome in children with early focal brain damage; 2) to determine whether epileptiform electroencephalographic (EEG) abnormalities in the FL population are stable over time, or get worse or better with time, and whether changes in the EEG over time correlate with changes in cognitive function; 3) to identify the extent and limits of plasticity in this population, and the role of seizures or epileptiform brainwave activity in limiting plasticity. Three groups of children between the ages of 8 and 12 years with pre- or peri-natal unilateral brain lesions in the middle cerebral artery distribution from stroke or hemorrhage, and matched controls, will receive neuropsychological, behavioral, and adaptive function assessments, including tests of intelligence, language, visual spatial skills, attention, memory, academic achievement, and executive function. Subjects will also have EEGs to assess the effects of epileptiform abnormalities on cognitive function, and brain MRI scans to determine the volume and location of the lesions. The 3 FL groups will consist of 20 children with a history of seizures, 20 children without seizures but with epileptiform EEG abnormalities, and 20 children with no seizures and normal EEGs. The results of these investigations should provide a better understanding of the role of seizures and epileptiform brain activity on cognitive function during brain development, as well as potential limitations on plasticity in the developing human brain. The findings may further serve as a basis from which to design more effective interventions for children at risk for cognitive dysfunction because of early brain damage.